In a spinning or twisting apparatus wherein a filament such as one or two yarns is wound up on a core in an automatic machine it is standard practice to feed each filament through a respective guide or traveler to the yarn core. This traveler can orbit about the respective core and can be moved axially along the core by an appropriate support structure. In order to prevent the turns of the filament from becoming enmeshed with each other it is standard practice to reciprocate the support for the travelers so that the turns are spaced from parallel turns and only overlie turns which they cross.
In an automatic machine a multiplicity of such travelers are jointly displaced along the respective cores so as simultaneously to form a multiplicity of bobbins or yarn packages. To maximize production it is obviously necessary to wind the yarn as fast as possible, yet nonetheless to avoid such a high speed that the yarn breaks. Practice has shown that in the middle region of the yarn package or bobbin being formed the speed can be at a maximum whereas in the end region it must be reduced somewhat to avoid breakage. These speeds are determined by the type of yarn, its fineness, and various other factors.
At the end of each winding operation the guide for the travelers through which the respective yarns passes is dropped down to a level below the core being wound so as to wind several turns of the yarn around the spindle carrying the core. Thereafter the core can be removed from the spindle with the yarn breaking between the core and the turns wound around it. In this manner the yarn is held firmly in place at the bottom of the spindle for the next winding operation.
A separate motor is normally responsible for dropping the traveler support down below the yarn core. Normally this is done at a relatively fast rate of speed, relative to the rotation rate for the yarn package, so that the last several turns are rather steeply wound around the exterior of the package. During this operation the main motor continues to operate, but once several turns have been wound around the bottom of the spindle a brake stops the yarn package from rotating.
Various factors must be taken into account at the end of the cycle to prevent too many or too few turns of the yarns from being wound around the respective spindles. The speed of the last stroke of the traveler support along the yarn body as well as the time at which the main motor is shut off, when the brake for the yarn is applied and the braking force must all be taken into account. Normally the rotation rate for the secondary motor, the time at which the main motor is shut off and the brake is turned on, and the braking force vary independently of each other.
The problem with this system is that its takes a relatively experienced operator to set the machine up to operate properly for a given yarn. Any mistakes in the setting can result in ruining the yarn packages and considerable down time for the winding machine.